Thermal pipe insulation

ABSTRACT

Improved thermal-insulating material of the type containing mineral wool and an organic binder are rendered smokeless by the inclusion of small amounts of activated carbon particles. The thermal-insulating material is particularly suitable for use as a thermal insulation pipe covering.

Umted States Patent 1 1 1111 3,909,347 Warren 1 1 Sept. 30, 1975 15 1 THERMAL PIPE INSULATION 3,149,023 9/1964 Bodendorf et a1. 162/181 R 3,269,889 8/1966 Hutchins 162/181 R 1751 inventor: -F Lee warren Aflmgto 3,682,667 8/1972 Roberts et a1. 162/145 He1ghts, I11.

[73] Assignec: United States Gypsum Company Primary E.\'am1'nerS. Leon Bashore Chlcago* Assistant E.\'aminerPeter Chin 22 Filed; Mar. 8, 1974 Attorney, Agent, or FirmKenneth E. Roberts, Esq.;

Stanton T. Hadley, Esq.; Samuel Kurlandsky [21] Appl. No.: 449,222

1521 11.5.01. 162/152; 161/170; 162/171; 1 1 ABSTRACT 162/172; 162/181 R 151 1111. C1. D2lD 3/00; 0211-" 11/00 1 1 1 fii f g f 35.": type [58] Field of Search 162/141, 145, 152, 181 R, dammg mm P I are 162/171 172' 161/170 cred smokeless by the me USIOII 0 311121. amqunts of activated carbon particles. The thermal-msulatmg ma- References Cited tertal 1s part1cu1ar1y sultable for use as a thermal 1nsu- 1at1on p1pe covermg. UNITED STATES PATENTS A 3,034,947 5/1962 Conlisk et a1 .1 162/181 A 7 Claims, N0 Drawings THERMAL PIPE INSULATION BACKGROUND OF THE INVENTION This invention relates to improved thermal-insulating material for use at temperatures in excess of 500F., and more particularly to improved thermal-insulating material of the type containing mineral wool and an organic binder and which can be particularly utilized as a thermal-insulation pipe covering.

Pipe coverings of the prior art have generally been provided as either loosely integrated fibrous or granular material, such as mineral wool, glass wool and the like, or flexible felts in mat or ribbon form, such as wool or hair felt, provided with a wrapping material to hold the bulk in place when wrapped about the pipe; or in fabricated molded or cast rigid forms such as of various asbestos, mineral wool and the like compositions held together in substantially rigid form by a ceramic inorganic binder. In this latter form of pipe insulation, the cost of ceramic inorganic binders contributes to making the product too expensive for extensive utilization as a pipe insulation material.

It is much more common in high-temperature insulation blocks utilized for other purposes to form a cast or water-felted sheet, mat or slab of mineral wool and the like inorganic fibrous constituents held together in substantially rigid form by an organic binder. Thus Cadotte US. Pat. No. 3,510,394 discloses mineral wool boards held together by a starchbased cellulosic binder. Roberts US. Pat. Nos. 3,379,608 and 3,379,609 refer to various water-felted inorganic fibrous heat insulation products utilizing a different water-activated nonfibrous cellulosic binder. However, certain problems have arisen when it was attempted to utilize such products for usage as thermal pipe insulation. Principal among these problems is that as the insulation material in contact with the hot pipe becomes heated, a temperature is reached where the organic constituents burn off. Generally this is accompanied by a malodorous stench; punking; and invariably accompanied by the emission of copious amounts of smoke. The emission of smoke in particular has been found in practice to render the usage of such materials as thermal pipe insulation impractical.

SUMMARY OF THE INVENTION Accordingly, one object and advantage of the present invention is the provision of fibrous insulation material, for use at temperatures above about 500E, which insulation material contains organic binders and other organic constituents, yet which material does not emit objectionable smoke, odors and the like.

Another object of this invention is the provision of thermal pipe insulation in substantially rigid form comprising a mineral wool product of the type having mineral fibers bonded by an organic binder, without accompanying emission in use of noxious vapors, objectionable smoke, or punking.

Still another object of this invention is the provision of heat-insulating mineral wool products of the type having mineral fibers bonded by an organic binder, wherein the product may be utilized as a thermal insulation at temperatures between about 500 to about 1,000F. without substantial emission of noxious vapors, objectionable smokeor punking.

The fulfillment of these and other objects and advantages of the present invention are accomplished by including, in a heat-insulating mineral wool product of the type having mineral fibers held together in a rigid form by an organic binder, of small amounts of activated carbon particles. This result is all the more surprising because activated charcoal itself is combustible and heretofore it was thought that its inclusion in such a formulation would be merely adding fuel to the fire, so to speak. Differential thermal analysis of the activated carbon particles showed that the material is combustible at about 840F., yet surprisingly its incorporation into such mineral wool products completely inhibits the emission of noxious odors and smoke at temperatures up to 1,000F.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The activated charcoal may be any of the carbon, char or charcoal produced by destructive distillation of wood, peat, lignite, nut shells, bones, vegetable or carbonaceous matter activated as is usually achieved by heating to temperatures of about 800900C. with steam or carbon dioxide to bring about a porous particle structure. Either the wood-based or coal-based activated charcoal is preferred, and it does not appear to make any difference which is used; and thus the carbon content of the activated charcoal may vary widely. Further, the activated charcoal may be of widely varying density, as generally available from 0.08 to about 0.5, and structural hardness, and neither characteristic appears to be of any particular importance to the present usage. However, it has been found that the porosity of the particles does make a difference in the performance for this use, and it is preferred that higher porosities be utilized as generally exhibited by larger sized particles. Thus, particle size of about by 325 US. Standard mesh sieve particles have been found satisfactory, and particles of about 50 by 325 mesh are especially preferred. While particles of somewhat greater or lesser size would be suitable for the use herein, it has been found that particles of greatly larger or smaller size are not satisfactory.

The amount of the activated charcoal to be utilized will generally depend upon the amount of organic binder and other organic constituents in the mineral wool product and will be present in an amount that is from about one-half of to equal to the amount of organic constituents of the product. Thus, in general it is preferred that amounts of about /2 to about 5 percent by weight of the total product be utilized based upon preferred mineral wool products containing generally about 3-10 percent organic binder and other organic constituents such as a wax. Accordingly, if greater or lesser amounts of organic constituents are present in the mineral wool product, the quantity of activated charcoal to be incorporated will vary directly therewith.

The precise composition of the particular mineral wool insulation product employed is not critical to the invention provided that they may contain generally from about 3 to about even 30 percent by weight of cellulosic binder or other organic constituents. For example, suitable mineral wool insulation product for use in the present invention may contain from about 5 to about percent by weight of mineral wool and from about 3 to about 30 percent by weight of cellulosic binder or other organic binder constituents. The mineral wool product is generally formed by water casting or water felting an aqueous slurry of mineral wool and the other ingredients, although other means may be used. The mineral wool used in the products of the present invention comprise fibers formed in well known and conventional employed mineral wool production processes from blast furnace slag and the like. The precise composition of the particular mineral wool fibers utilized is not critical to the invention. Although many different organic binders generally of a cellulosic nature would be suitable for use in the present invention, a preferred form of such binder is a non-fibrous water-activated cellulosic binder prepared by forming a slurry or furnish of cellulosic material, preferably of unbleached waste kraft paper. The slurry is then gelatinized by passing it through a series of refining and gelatinizing steps to obtain a suitable freeness. It has been found that a preferred water-activated cellulosic binder of this type for forming the mineral wool product has a Schopper-Riegler freeness of less than 100, and preferably less than 90. Other organic constituents entering into the formulation of the products of the present invention may come from optional ingredients added to obtain superior processing and product characteristics for the basic mineral wool product, as by the inclusion of a wax or wax emulsion to serve as a sizing to stabilize the material in high-humidity storage conditions. The wax may be employed in amounts up to about 2 percent by weight, although preferably comprising from about 0.25 to about 1 percent. The wax utilized is usually in the form of an emulsion or dispersion, and may be one or more of several varieties, such as, for example, microcrystalline, refined paraffin, petroleum, synthetic waxes, etc. A particularly preferred emulsion would comprise about 50 percent asphalt and about percent wax, by weight. Other optional ingredients include for example a fusible ceramic clay, preferably non-swelling and having a high proportion of silica and alumina, such as fire clay, ball clay or the like present in an amount at least equal to about the amount of organic binder, so as to serve adequately as a binderreplacement at elevated temperatures. As the mineral wool products containing an organic binder become heated to a high temperature, the organic binder and the wax-asphalt emulsion if present burn out; however, the high temperature causes the clay to fuse and thus to serve as a binder which gives the material continued strength and basic form.

ln addition to the components mentioned above, the compositions may optionally contain certain additives for optimum properties and processing characteristics. For example, alum for sizing and perlite fines or clay pellets to adjust product density may be included in the formulation, depending upon the product characteristics desired. Some perlite may be included where higher hardness levels are desired in the product, and thus preferably about 10-20 percent of perlite may be employed, generally utilizing the well-known thermally expanded product which is available in a variety of mesh sizes. Obviously other materials may also be employed such as boric acid or sodium borate may be used in amounts up to about 6 percent by weight, and preferably from about 2 to 5 percent to impart even better fire resistance, which materials generally do not provide any impact with reference to inhibiting smoking and odors.

This invention will now be further described by reference to specific examples for the purpose of further illustrating and disclosing the present invention, and the examples are in no way to be construed as limitations thereon.

A convenient and meaningful test evaluation of smoke emission is by means of a small pot test" utilizing about 6 inch by 6-7 inch by 1 inch thick samples of the material to be evaluated. For this test a Hoskins furnace or equivalent pot furnace having a 5 inch diameter and 5 inch furnace depth is equipped with a Wheelco controller set for 1,000F. A thermocouple is centered at the very top of the furnace and covered by a previously fired piece of ceramic material to cover the whole furnace surface plus about an extra 1 inch area, and the furnace is heated up to l,O00F. When the l,OOOF. temperature is reached, the prefired piece of material is quickly taken off the furnace and the test sample put in its place during a time of a couple of seconds. A high-temperature thermometer is placed on top of the test sample to measure the outside surface temperature of the test sample and a timer is started. The controller maintains the temperature at 1,000F. on the underside of the test sample, as measured by the thermocouple. The outside surface temperature as measured by the thermometer begins to rise as the sample piece is heated by the furnace. There is generally a jump in the outside surface temperature due to the burning of the organics, and after the organic constituents of the test sample have burned away the outside surface temperature thermometer reading drops; and this peaking of the outside surface temperature is used as a measurement of the end of the test. Generally the test time is about 19-24 minutes depending upon the quantity of organics in the test sample. Throughout the test empirical observations are made of any odor given off by the test sample and of any visible smoke given off by the test sample. A black background is placed around the furnace and test sample to increase visibility of smoke. The time of any smoking interval is noted during the test.

In addition a 1,000F. hot pipe test apparatus has been utilized to provide an accurate simulation of severe field service conditions for pipe insulation samples. For the hot pipe test, a 57 /2 inch long section of 6 inch inside diameter and about 7 inch outside diameter steel pipe is provided, on the inside of the pipe, with radiant heating elements spaced equidistantly to provide uniform heating the length of the pipe. The heat ing elements, such as a Chromalox commercial heating element, are spaced down the center of the inside of the pipe and supported by pieces of refractory material, Spaced behind the pipe is a sheet metal background painted black and illuminated by spotlights to aid in 0bserving visible smoke. The test samples to be evaluated are placed around the pipe, covering a three-foot section of the pipe, and the heating elements are activated to start the test. The insulation is then observed for visible smoke and odor while the temperature, measured by a series of thermocouples, is brought up to l,O0OF. and maintained there for about 22 minutes for one-inch samples. Samples thicker than one inch were tested for about 60-90 minutes.

If no visible smoke, or only intermittent infrequent wisps of smoke are observed during the above tests, the sample evaluated is considered to be a successful solution for non-smoking l,O0OF. pipe insulation.

EXAMPLE 1 Test samples of mineral wool insulation material were formulated to contain the following ingredients and proportions:

57.5 percent slag derived mineral ,wool;

percent expanded perlite;

15 percent ball clay;

6 percent anhydrous sodium borate;

0.5 percent wax-asphalt emulsion; and

6 percent water-activated cellulosic binder. Thus; the samples contain 6 /2 percent organic constituents in the cellulosic binder and wax emulsion. To some of the samples was also added 3 percent by weight of 80 by 325 mesh Nuchar brand of activated charcoal available from Westvaco, Covington, Va.

A number of the above samples were submitted to a differential thermal analysis measurement, and it was found that a high temperature, or exotherm, existed at 610F. for samples without the activated carbon; and samples containing activated carbon exhibited no major peaks but a number of small temperature peaks, principally at about 590F. and at 930F. Differential thermal analysis of a sample of the activated carbon alone showed that the material completely ignited. The exotherm started at 840F. and passed through 1,000F.

Replicate samples of the above formulation were submitted to the pot furnace evaluation. In the control formulations not containing the activated charcoal particles, a large amount of smoke was generated through the first l 1 minutes of the test and then a small amount of smoke continued to be emitted until 21 minutes into. the test, at which time the temperature peaked and the test was concluded. In samples utilizing the 3' percent by weight of 80 by 325 mesh particles, only very light smoke was observed for the first l minute and 15 seconds, and there was no visible smoke thereafter. The temperature peaked at 24 /2 minutes and the test was concluded. In a companion comparison using the same amount of the same activated charcoal but sized to 50 by 325 mesh, only two or three very hard to see wisps of smoke were emitted in the first few seconds; and there was no visible smoking thereafter. The temperature peaked at 23 minutes and the test was concluded.

Exemplary examples of the above formulations were submitted to the hot pipe test and evaluated to simulate severe field service conditions. The samples containing the activated charcoal of '80 by 325 mesh produced a very small amount of smoke for a few minutes and were judged acceptable. The control comparison sample not including the activated charcoal produced at least 20 times more smoke. Further in comparison, an equivalent formulation utilizing the 50 by 325 mesh activated charcoal in the same amount did not smoke at all while the pipe temperature was increased to l,OOOF.' and did not punk during this time nor give off any detectable odors.

EXAMPLE 2 Exemplary results of the samples evaluated on the hot pot test utilizing varying amounts of organic binder and optional wax-asphalt emulsion, and varying amounts of differing activated charcoal particles are set forth as follows:

TABLE Organic Constituents Activated Charcoal Observations 2% starch binder 2% Nuchar 65 brand derived from coal or peat; 80 X 325 mesh;

density: 29 lb./cu,ft.;

moderate smoke for seconds;

wisps continuing until 1% minutes;

no smoke thereafter; temperature peaked at 20 minutes.

having Iodine N0. 950

3% water-activated cellulosic binder charcoal;

80 X 325 mesh 3% coal derived 80 X 325 mesh;

3% water-activated cellulosic binder 3% wood based activated small wisps of smoke intermittently for 1 minute; no smoke thereafter; temperature peaked at 21 minutes. no visible smoke at any time;

temperature peaked at 18 minutes.

29 lb./cu.ft. density; Iodine N0. 950

3% water-activated cellulosic binder plus k7c wax-asphalt emulsion 3% Pittsburgh Activated Charcoal Division of Calgon brand; 8() X 325 mesh no visible smoke at any time; temperature peaked at 18 minutes.

3% water-activated cellulosic binder plus &7 wax-asphalt emulsion 4% water-activated cellulosic binder plus 127! wax-asphalt emulsion 6% water-activated cellulosic binder plus 15% wax-asphalt emulsion 6% water-activated cellulosic binder plus wax-asphalt emulsion 7% water-activated cellulosic binder plus 5670 wax-asphalt emulsion 7% water-activated cellulosic binder plus 1&% wax-asphalt emulsion 7% water-activated cellulosic binder plus /&% wax-asphalt emulsion 2% derived from coal;

80 X 325 mesh;

25 lb./cu.ft. density; Iodine No. 950

3% Nuchar brand derived from coal; 80 X 325 mesh; 29 lb./cu. ft. density; Iodine N0. 950

3% 20 X mesh;

35 lb./cu.ft. density; Iodine No. 850

3% 20 X 50 mesh;

25 lb./cu.ft. density;

Iodine N0. I050 3% Nuchar brand derived from coal;

50 X 325 mesh;

29 lb./cu.ft. density;

Iodine N0. 950

same amount of same material immediately above, but screened to retain only 50 X 200 mesh same amount of same material immediately above, but screened to retain only 50 X mesh wisps of smoke for l minute and I5 seconds; no smoke thereafter; temperature peaked at 19 minutesv no visible smoke at any time; temperature peaked at 20 minutes,

wisps for l minute; no visible smoke any time thereafter; temperature peaked at 24 minutes.

light smoke for 1% minutes; no visible smoke thereafter; temperature peaked at 24 minutes.

It is readily apparent from the above description of the invention that various modifications of the particular materials utilized herein may be made within the scope of the invention. For example, many different additives may be incorporated into the mineral fiber product to impart particular product characteristics and processing attributes. Therefore, the invention is not to be limited to the specific details described herein, except as may be required by the following claims.

What is claimed is:

1. An improved heat-insulating mineral wool product of the type having mineral wool fibers bonded into a coherent mass by an organic binder, wherein the improvement comprises the inclusion of activated charcoal particles present in an amount of about V2 to about equal to the amount of organic constituents of the product.

2. An improved heat-insulating mineral wool product according to claim 1, wherein the activated charcoal particles are of a size of about 50-80 by 200-325 mesh.

3. An improved heat-insulating mineral wool product according to claim 1, including from about 1 to about 8 percent by weight of starch binder and from about /2 to about 5 percent by weight of activated charcoal.

4. An improved heat-insulating mineral wool product according to claim 1, including from about 4 to about 8 percent by weight of water-activated cellulosic binder and from about 2 to about 5 percent by weight of activated charcoal particles.

5. An improved heat-insulating mineral wool product according to claim 1, including about 40-65 percent by weight of mineral wool, from about 3 to about 8 percent by weight of water-activated cellulosic binder, about /2 percent of wax-asphalt emulsion; and from about 1 to about 5 percent by weight of activated charcoal particles.

6. A thermal insulating pipe insulation material of non-smoking characteristics comprising from about 40 to about percent of mineral wool; from about 1 to about 10 percent or organic constituents, principally cellulosic binder; and from about V2 to about 5 percent of activated charcoal particles.

7. A method of making a non-smoking thermal insulating material suitable for use as a covering for pipe comprising the steps of adding to an aqueous slurry of mineral wool fibers and organic binder an amount of activated charcoal of about /2 to about equal the amount of organic constituents; forming a sheet therefrom; and drying said sheet. 

1. AN IMPROVED HEAT-INSULATING MINERAL WOOL PRODUCT OF THE TYPE HAVING MINERAL WOOL FIBERS BONDED INTO A COHERENT MASS BY AN ORGANIC BINDER WHEREIN THE IMPROVEMENT COMPRISES THE INCLUSION OF ACTIVATED CHARCOAL PARTICLES PRESENT IN AN AMOUNT OF ABOUT 1/2 TO ABOUT EQUAL TO THE AMOUNT OF ORGANIC CONSTITUENTS OF THE PRODUCT.
 2. An improved heat-insulating mineral wool product according to claim 1, wherein the activated charcoal particles are of a size of about 50-80 by 200-325 mesh.
 3. An improved heat-insulating mineral wool product according to claim 1, including from about 1 to about 8 percent by weight of starch binder and from about 1/2 to about 5 percent by weight of activated charcoal.
 4. An improved heat-insulating mineral wool product according to claim 1, including from about 4 to about 8 percent by weight of water-activated cellulosic binder and from about 2 to about 5 percent by weight of activated charcoal particles.
 5. An improved heat-insulating mineral wool product according to claim 1, including about 40-65 percent by weight of mineral wool, from about 3 to about 8 percent by weight of water-activated cellulosic binder, about 1/2 percent of wax-asphalt emulsion; and from about 1 to about 5 percent by weight of activated charcoal particles.
 6. A thermal insulating pipe insulation material of non-smoking characteristics comprising from about 40 to about 80 percent of mineral wool; from about 1 to about 10 percent or organic constituents, principally cellulosic binder; and from about 1/2 to about 5 percent of activated charcoal particles.
 7. A method of making a non-smoking thermal insulating material suitable for use as a covering for pipe comprising the steps of adding to an aqueous slurry of mineral wool fibers and organic binder an amount of activated charcoal of about 1/2 to about equal the amount of organic constituents; forming a sheet therefrom; and drying said sheet. 